Page 1434 - Cote clinical veterinary advisor dogs and cats 4th

Osteosarcoma 727

Initial Database procedure), with biopsy submission after • The most commonly used adjuvant chemo-
surgery.
Radiographic imaging of OSA: • CT imaging is recommended for axial tumors therapy drug is carboplatin. Cisplatin and
VetBooks.ir neoplasia and infection, and they are char- to more accurately stage local disease and typically include one or more of these drugs Diseases and Disorders
doxorubicin also have efficacy. Protocols
• Aggressive bone lesions are associated with
acterized by one or more of the following
help with planning surgery and/or radiation
for a total of 4-6 treatments.
radiographic signs:
disease progression in some dogs with visible
○ Presence of bone disruption, particularly therapy (RT). If CT is performed, lungs • Toceranib phosphate (Palladia) can help slow
should be included in imaging to screen
involving the cortex for pulmonary metastasis. pulmonary metastasis.
○ Bone lysis; permeative and moth-eaten • Whole-body bone survey radiography and • A genetically engineered Listeria-based
patterns always are aggressive; geographic nuclear scintigraphy (i.e., bone scan) are vaccine has been developed that targets
lysis can be aggressive or benign. not routinely recommended; however, any ERBB2 (HER2/NEU), an oncogene expressed
○ Nonhomogeneous, interrupted periosteal suspicious lesions or painful areas should be on some canine OSAs. This vaccine has been
bone formation, or amorphous new bone imaged. used in combination with amputation and
deposited haphazardly in the soft tissues carboplatin. The vaccine is not commercially
surrounding the bone TREATMENT available at the time of publication.
○ Ill-defined or indistinct transition zone • A variety of palliative treatments can be used
between normal and abnormal bone Treatment Overview to help control the pain associated with the
• Appendicular OSA is usually located in the Definitive treatment includes surgery or stereo- primary tumor. Multimodal therapy is more
metaphyseal region of long bones. Extension tactic radiosurgery (SRS) for the primary tumor, effective, and pain is easier to prevent than
across joints is uncommon. followed by adjuvant chemotherapy to help reverse.
After a radiographic or histologic diagnosis, delay the onset of visible metastasis. Palliative ○ Nonsteroidal antiinflammatory (NSAID)
animals should be completely staged: therapy focuses primarily on pain control and choices (use only one at a time) include
• CBC, serum biochemistry panel, urinalysis is indicated when patients present with gross aspirin 10-25 mg/kg PO q 8-24h,
• Three-view thoracic radiographs metastatic disease or owners decline definitive carprofen 2 mg/kg PO q 12h, deracoxib
○ <10% of animals have visible pulmonary therapy. 1-2 mg/kg PO q 24h; may use 3-4 mg/kg
metastatic lesions at initial diagnosis. PO q 24h for first 7 days only, meloxicam
○ Most dogs with OSA ultimately develop Acute and Chronic Treatment 0.1 mg/kg PO q 24h, and firocoxib 5 mg/
visible metastatic disease, even if the • Surgical removal of the primary tumor kg PO q 24h.
primary tumor is surgically removed, ○ Amputation is the standard treatment for ○ Other oral analgesic drugs include
indicating metastasis occurred before appendicular OSA. Most animals function acetaminophen with codeine (Tylenol #4
initial presentation. well after surgery; osteoarthritis is rarely [300 mg acetaminophen, 60 mg codeine])
• <5% of dogs have lymph node metastasis, a contraindication. 0.5-2 mg/kg PO q 6-8h with dosing based
but any enlarged regional lymph nodes ○ In limb-sparing techniques, only the on codeine (acetaminophen is contrain-
should be evaluated with cytology and/or neoplastic portion of the affected bone dicated in cats), tramadol 2-5 mg/kg PO
histopathology. is excised, and the weight-bearing axis is q 6-12h, gabapentin 10-15 mg/kg PO q
re-established using a variety of strategies. 8-12h, amantadine 3-5 mg/kg PO q 24h.
Advanced or Confirmatory Testing Candidates should have tumors arising ○ Bisphosphonates decrease bone resorption
• Fine-needle aspiration (FNA) with cytologic from the distal radius, distal ulna, or and increase bone mineral density.
analysis is minimally invasive and can help proximal femur, and the tumor should ■ Pamidronate 1-2 mg/kg IV q 3-4 weeks
support a diagnosis of OSA. involve < 50% of the bone, with minimal decreases lameness in 30% of dogs.
○ FNA can be considered for lesions with extension into the surrounding soft tissues. ■ Zoledronate 0.1 mg/kg IV q 4 weeks
associated cortical destruction. Ultra- ■ Compared with amputation, survival decreases lameness in 75% of dogs.
sound guidance can be used for sample times are similar, but complication rates ○ Palliative RT reduces pain in 75%-90%
collection. are higher (infection, implant failure, of dogs with OSA. Analgesia persists for
○ Cytologic analysis can distinguish between local tumor recurrence). a median of 2-3 months.
malignant and nonmalignant lesions with ○ For animals with axial OSA, wide surgical ○ Animals with pulmonary metastasis often
an accuracy of 70%-85%. In samples excision is recommended whenever pos- benefit from oral glucocorticoids at anti-
diagnostic for cancer, alkaline phosphatase sible. Complete excision is often more inflammatory doses, such as prednisone
cytochemistry is a highly sensitive and difficult because of the tumor’s proximity 0.5-1 mg/kg PO q 24h (do not combine
fairly specific marker for OSA and can to vital structures. When complete excision with NSAIDs).
help distinguish OSA from other bone is not possible, surgery can be combined
tumors. with conventional RT, or SRS can be Recommended Monitoring
• Histopathologic evaluation is required to considered in place of surgery (see below). Clinicians should evaluate patients every
definitively diagnose OSA. • SRS is a specialized form of RT in which a 2-3 months for evidence of local recurrence
○ An incisional biopsy can be performed large dose of radiation is precisely delivered and metastatic disease. Ideally, this includes
using a Jamshidi bone biopsy needle. to the primary tumor, usually in 1-3 daily a thorough physical exam and three-view
Tumors are distinguished from benign treatments. Candidates should have minimal thoracic radiographs. Imaging of the site of the
lesions with an accuracy of 90%; the cortical lysis to minimize risk of subsequent primary tumor may be indicated, depending on
specific tumor type is diagnosed with an pathologic fracture. location, completeness of excision, and clinical
overall accuracy of 80%. ○ Compared with amputation, survival signs.
Biopsy core(s) should be taken from the times with SRS are similar. In contrast,
■
lesion’s center. Samples taken from the conventional RT is inferior to amputation. PROGNOSIS & OUTCOME
periphery are likely to be nondiagnostic, ○ SRS also can be used for axial tumors that
containing only reactive bone. are not amenable to surgery. However, • Most animals with OSA ultimately succumb
○ If signalment, history, and initial database because OSA contains bone mineral, the to the effects of the primary tumor and/or
all support a diagnosis of OSA, and the extent of tumor shrinkage and return to metastatic disease.
owners are willing to treat aggressively, function varies for vertebral tumors and ○ The lungs are the most common site for
it is reasonable to surgically remove local other tumors compressing adjacent normal metastasis, followed by other bones and
disease (amputation or limb-sparing structures. then various soft tissues.
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